I see you took the former route. To be a “true” plugin (meaning just drop in and activate) many of the plugins insert code into every page regardless of whether or not it is needed so you don’t have to edit additional files.
In the case of this plugin, it inserts the css for the form in the header of each page using the add_filter, instead of saying, “Activate the plugin and add this css into the file called style.css”.
I prefer to have most, if not all, of my css “stuff” in style.css. So what I was suggesting was to put a “//” in front of the add_filter so that it would not run. Then copy all the css in the plugin into your style.css. Essentially all that does is remove the css from your header and puts it into your style.css thus you don’t have to go to the plugin each time you want to make a change in the form layout. That’s all.